/*
 * Copyright 2014 mango.jfaster.org
 *
 * The Mango Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package org.jfaster.mango.util;

import java.math.BigInteger;

/**
 * @author ash
 */
public class HashUtil {

    private static final BigInteger INIT32  = new BigInteger("811c9dc5", 16);
    private static final BigInteger PRIME32 = new BigInteger("01000193", 16);
    private static final BigInteger MOD32   = new BigInteger("2").pow(32);

    public static int fnv1_31(String str) {
        BigInteger bi32 = fnv1_32(str.getBytes());
        return bi32.intValue() & 0x7fffffff;
    }

    public static int fnv1_31(long n) {
        return fnv1_31(String.valueOf(n));
    }

    private static BigInteger fnv1_32(byte[] data) {
        BigInteger hash = INIT32;

        for (byte b : data) {
            hash = hash.multiply(PRIME32).mod(MOD32);
            hash = hash.xor(BigInteger.valueOf((int) b & 0xff));
        }

        return hash;
    }

}
